The U.S. State Department said on July 21 that it is looking into reports that another Iranian-American has been detained in Iran.

Family members said Iranian authorities took Robin Shahini, 46, of San Diego, California, into custody on July 11 while he was visiting his sick mother in Iran and he has not been heard from since.

That same day, Iran announced the indictments of a Lebanese man and three dual nationals from Britain, Canada, and the United States on unspecified charges.

Shahini was most recently a student at San Diego State University, where he had been accepted into a graduate program in homeland security but had not as yet registered for classes that begin next month.

Family members told the Associated Press that they fear he was detained because of his online comments criticizing Iran's human rights record.

Iranian authorities took his personal belongings when they took Shahini into custody, his family said. He had a plane ticket to return to San Diego on July 25.